FIG. 1 presents a standard architecture of the demodulation of a modulated signal followed by an amplification of the demodulated signal obtained.
Such a standard architecture is for example implemented and described in the data sheet of UAA3515 from Philips semiconductors. In such architecture the demodulation is realized by a demodulator DEM using a conventional phase locked loop including a phase detector PDT, a loop filter LFI and a voltage controlled oscillator function VCO. Then the demodulated signal FDM is applied to a first amplifier stage G1 comprising a high gain amplifier G∝ and passive elements C1, R1 and R2. In integrated circuit technology, the use of passive elements generally implies the use of at least two connection pins P1 and P2 as shown in FIG. 1. Then the output of the amplifier stage G1 is conventionally connected using an intermediate filter INF to a second amplifier stage G2 including a complex gain control amplifier GGC. This second amplifier stage is then connected to a processor PRO that processes the signal so that this signal can be used.
Such architecture presents the drawbacks that two connection pins are needed, external components are needed that are found on a PCB and moreover impose their time constant (this time constant is even greater than the R1C1 multiplication and has to be high so as not to deform the audio signal), the presence is needed of a complex gain control amplifier that often deteriorate noise floor characteristics.